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In Natural Fluid Convection becomes dependant on Rayleigh number
and Prandtl number : LaTeX Math Inline |
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body | --uriencoded--\mbox%7BNu%7D = f (\mbox%7BRa%7D, \mbox%7BPr%7D) |
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.:
LaTeX Math Block |
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| \mbox{Nu}_D= \left[ 0.825 + \frac{0.387 \, \mbox{Ra}_D^{1/6}}{ \left[ 1+ (0.492/\mbox{Pr})^{9/16} \right]^{8/27}} \right]^2 |
| | All convection regimes in pipelines
LaTeX Math Inline |
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body | --uriencoded--\mbox%7BRa%7D_D \leq 10%5e%7B12%7D |
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LaTeX Math Block |
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| \mbox{Nu}_L= 0.68 + \frac{0.663 \, \mbox{Ra}^{1/4}}{ \left[ 1+ (0.492/\mbox{Pr})^{9/16} \right]^{4/9}} |
| | Laminar convection
LaTeX Math Inline |
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body | --uriencoded--\mbox%7BRa%7D \leq 10%5e9 |
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In case of natural convection in the annulus the Nusselt number becomes also dependant on the annulus geometry:
LaTeX Math Block |
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| {\rm Nu}_{ann} = \frac{2 \cdot \epsilon({\rm Ra})}{\ln (r_{out}/r_{in})} |
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where
Forced Convection
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In Forced Fluid Convection the Nusselt number becomes dependant on Reynolds number
and Prandtl number :
LaTeX Math Inline |
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body | --uriencoded--\mbox%7BNu%7D = f (\mbox%7BRe%7D, \mbox%7BPr%7D) |
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Both numbers have similar definition except that Nusselt number is based on thermal conductivity of the fluid while Biot Number is based on thermal conductivity of the solid body.
Normally, Normally Nusselt number indicates whether conductive or convective heat transfer dominates across the interface between solid body and fluid.
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